2010 Volume 20 Issue 2 Pages 21-26
The introduction of in vitro fertilization (IVF) and the molecular analysis of single cells has made it possible to perform preimplantation screening of human embryos for a variety of genetic disorders. Preimplantation genetic diagnosis (PGD), a very early form of prenatal diagnosis, offers the advantage of allowing the selection and transfer of apparently normal embryos, so that couples at risk of transmitting a serious genetic disease or structural chromosomal abnormalities to their offsprings can start a pregnancy without the anxiety of a possible termination or miscarriage. Since its introduction in 1990, PGD has become a practical option world-wide, and by the end of 2007 about 22,000 cycles of PGD had been reported resulting in over 3,000 unaffected babies. In Japan, its clinical application for the couples with genetic diseases was allowed under the approval of Japan society of obstetrics and gynecology in 2004, and, in addition, the reciprocal translocation carriers with recurrent miscarriages were permitted as one of indications in 2006. Although PGD for translocation carriers, which is performed using FISH usually, has been reported to allow statistically significant reduction in spontaneous abortions, on the other hand, there are still some technical problems to be resolved, which are mainly based on single-cell genetic analysis and the high frequency of mosaicism observed at the cleavage stage embryo.
